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4.0 SUBS�JRFACE INVESTIGATION 41 DRILLING On August 8 and 19, 1991 seven soil borings (B-1, B-2, B-3, SB-d, SB-5, VW-1 and VW-2) were drilled and sampled at the locations shown on Figure 2 Frve of the borings were drilled with truck- mounted drilGng equipment using 8-inch outside-diameter (OD) hollow-stem augers. Boring SB� and SB-5 were drilled with a custom-built drill rig also equipped with 8-inch OD hollow stem augecs. Ti�ic rig was ut�:+:d due to restricted :.ccess lunitations. All of t6e borings were drilled by McGarrett Drilling of Bellewe, Washington. Prior to each boring, the auger was steam-cleaned in order to prevent cross contamination between borings. ASEACOR geologist observed the drilGng and logged t6e borings. Soils were visually classified in acoordance with the Uni£ed Soil Classification System (LTS(S). Boring logs are presented in Append'uc A A two-inch inside-diameter split spoon sampter was driven by a 140-pound wire-line hammer at app*mdmately frn-foot intecvals to collect soil zamples. Before each use, the sampler was cleaned in an aqueous solution of Iiqui-Noz cleaaser, rinsed with tap water, and rinsed a second time with distilled, de'_ooized water. 'Ibis rigorous cleaning procedure was followed in order to prevent cross contamination between sample intecvals. Soil cuttings &om the bodngs were placed on plastic in a stcekpile located near the west side of the building. Soilc encountered during the drilling activides were predominantly composed of brown gray saAds with gravel and cobbles. The very dense soils lacked signi6cant ocganics and were dry to moisL Groundwater was not encountered during drilling in any of the borings. From the drive samples, soil samples were colixted for c6emicr.l analysis by transferring soil to sampl.e containecs using a clean stainless steel scoop. The scoop was cleaned pri�r to the traasfer of each sampk using the same procedures as that for the split spoon sarapler. The sample container from esch sample interval was sealed with Te4on-lined screw caps, labeled, wrapped with tape, and immediately placed in a 5eid cooler with ice. Remaining soil was checked for hydrocarbon odo[s and monitored for wlatile organic vapots using a photoionization detector (PID). The PID was equipped' with a 10.2 electron-volt lamp and calbrated,in the field with isobutylene (a benzene equivalent standard gas). PID readiags ate tecorded on the boring logs in Appendiz A 4.2 VADOSE ZONE WELL INSTALLATION Upon compleiion, two borings (VW-1 and VW-2) were wnverted to monitoring welLs. Each well was completed using two-inch-diameter, flush-threaded, Schedule 40 PVC, slotted (0.010-inch slots) and blank casing. Tt�e bottom of the casing was sealed with a solid PVC cap, and the top was covered with locldng plug-type cap. The annular space between borehole wal: and casing was bac�lled with clean filter sand from the bottom of the borehole to appro�dmately 2 feet above the slotted interval, and a 2-foot-thick bentonite seal was placed above the gravel pack. The temainder of the annulus was filled with a bentonite-cement grout to a point just below the ground surface. M.ua�.arrn n�� tz �„i 4-1